Abstract As a renewable fuel, ammonia NH3 is identified as one of the most potential candidates to tackle greenhouse gas challenge. For this, ammonia-hydrogen-oxygen combustion in micro-power systems is numerically investigated in this work. The computational model is first validated with experimental data available in the literature. Then, emphasis is placed on the effects of (1) the fuel composition ratio e (defined as the hydrogen molar fraction relative to the mixed fuel of ammonia and hydrogen) and (2) the wall thermal conductivity (WTC) on the system's working performance. Results indicate that increasing e can not only lead to the outer wall temperature (OWT) and radiation efficiency (RE) being decreased, but also enable the flame propagate towards the combustor inlet. An optimized e is found to minimize the NOx emission by approximately 54.9% compared to 100% NH3 combustion. Further analyses show that a high WTC has a potential to increase OWT at low fuel flow rates, while RE varies non-monotonically with the NH3 volumetric flow rate. It is also shown that WTC has a slight effect on NOx emission and the flame shape. This work sheds light on a simple but effective way to improve thermal and emission behaviors.

中文翻译：

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燃料成分和壁面导热系数对氨/氢-氧微动力系统热性能和NOx排放性能的影响

摘要 作为一种可再生燃料，氨 NH3 被认为是应对温室气体挑战的最有潜力的候选者之一。为此，本文对微动力系统中的氨-氢-氧燃烧进行了数值研究。该计算模型首先用文献中可用的实验数据进行验证。然后，重点放在（1）燃料组成比e（定义为氢摩尔分数相对于氨和氢的混合燃料）和（2）壁面热导率（WTC）对系统工作性能的影响. 结果表明，增大 e 不仅会导致外壁温度 (OWT) 和辐射效率 (RE) 降低，而且会使火焰向燃烧器入口传播。发现优化的 e 与 100% NH3 燃烧相比，可将 NOx 排放量减少约 54.9%。进一步的分析表明，高 WTC 有可能在低燃料流量下增加 OWT，而 RE 随 NH3 体积流量非单调变化。还表明 WTC 对 NOx 排放和火焰形状有轻微影响。这项工作揭示了一种简单但有效的方法来改善热和发射行为。